The demand for diopter-adjustable single-lens reflex finders has grown steadily in recent years in the wake of the popularization of cameras (such as single-lens reflex cameras) for older age groups. To meet this demand, eyepiece lenses have been proposed that comprise a negative lens group, a positive lens group and a negative lens group arranged in this order, from an eyepoint side, along the optical axis, and in which diopter can be adjusted by moving the positive lens group (for instance, Japanese Unexamined Patent Application Laid-open Nos. H09-329752 and 2000-171731).
However, eyepiece lenses having such a constitution are problematic in that, for instance, the eyepiece lens of the optical system disclosed in Japanese Unexamined Patent Application Laid-open No. H09-329752 comprises 4 to 5 lenses, which drives up costs. The optical system disclosed in Japanese Unexamined Patent Application Laid-open No. 2000-171731 is also problematic, for instance, in having a short eye relief and low finder magnification.